The research focus is on the acoustic and perceptual correlates of the compromised speech intelligibility that is common throughout the lifespan in persons with disorders such as Down syndrome (DS), cerebral palsy (CP), hearing impairment, autism, and a variety of genetic disorders. The proposed project aims to address NIDCD?s priority to better understand the natural history of communication disorders throughout the lifespan in Down syndrome, specifically this proposal aims to establish the lifespan patterns of speech intelligibility and its acoustic and perceptual correlates in individuals with DS (ages 4 to 53 years), with comparisons to the patterns observed in a control group with typically developing (TD) speech. The findings will provide the knowledge base needed to inform and guide the clinical management of communication disorders throughout the lifespan in individuals with Down syndrome, hence addressing another NIDCD priority. To date, there is no evidence-based treatment guidance for DS (e.g., none listed in the Practice Portal of the American Speech-Language-Hearing Association) even though enhancing speech intelligibility, as a means to improve communication, is a high priority treatment goal that parents and others seek for individuals with DS. The ability to communicate is central to educational, vocational and social interactions, and reduced speech intelligibility can severely restrict these interactions and adversely affect quality of life. The goal of improved intelligibility through the lifespan is made all the more important given that the average lifespan for persons with DS has increased remarkably owing to improved health care. The speech disorder that underlies speech intelligibility in DS is particularly difficult to analyze because it is associated with multiple factors, including, but not limited to, craniofacial dysmorphologies (shortened midfacial skeleton), laryngeal dysmorphology (laryngomalacia), motor impairments (dysarthria and/or apraxia) phonological delay or disorder, dysfluency, and hearing impairment (Kent & Vorperian, 2013). The parent award, supporting the Vocal Tract Development Laboratory (VTLab) research, is studying the craniofacial dysmorphology in DS and CP as a means to understand the role of function (breathing, deglutition and speech) in shaping the anatomic structures in TD individuals during the course of development and across the lifespan (i.e. ?functional anatomy? is an important focus of the parent award). In addition, the VTLab is studying the biological basis of speech development and production in typically and atypically developing speech, and for that purpose has collected a large and unique set of high-quality speech recordings from individuals with DS and TD individuals across the lifespan to examine anatomic-acoustic correlates. For this stated purpose, the VTLab has completed making vowel acoustic measurements from all the TD and DS monosyllabic word recordings and obtained intelligibility ratings on all DS recordings (words and sentences). This supplement provides a natural extension to our work to date, providing a unique opportunity to capitalize on parent award available resources of high quality speech recordings (including vowel prolongations, monosyllabic words, and sentences), as well as intelligibility ratings of words and sentences (obtained from a panel of 5 listeners) to immediately embark on investigating a broad range of speech production and voice quality measures, including both acoustic measures and perceptual ratings, related to speech intelligibility. The data collection protocol used is well-suited to the proposed systems-based approach for speech production where the acoustic and perceptual analyses will examine each of the major subsystems individually, as well as their interactions. The ultimate aim of this application is establishing acoustic-perceptual correlates of speech intelligibility using a lifespan perspective (to our knowledge there is no precedence to this approach). The results are expected to provide a foundation for speech assessment and intervention strategies in individuals with DS.